Process for treating mineral oils



sept.1,1li1936.l v 11R. FENSKE ETA.; 2,052,971

PROCESS FOR TREATING MINERAL oILs Filed Nov. 1.25, 19253 '7 Sheets-Sheet 1 SM Alg@ M. r-z.v FgNsKE Er AL. 2,052,971 PROCESS FOR TREATING MINERAL OILST" l Sept.; I,v

Filled Nov. 15, 1933 lfflY'Stumm-Sheet 2 uvz/Juny a? u L 1MM/40nd Sept. 1, 1936. M. R. FENsKE E-r Ax.

I PROCESS FOR TREATING MINERAL OILS 7 sheets-sheet 4 me/Wto mK NVN mn Filed Nov. 13, 1933 um R f m H H n H H .w J Y u1 u.. u1 uw u.t k. u u1 n H H Sept. 1, 1936.

M. R. FENSKE r-:T AL

PROCESS FOR TREATING MINERAL OILS Sept- 1, 1936- M. R, FENSKE ET AL 2,052,971

PROCESS FOR IREATING MINERAL OILS 7 Sheets-Sheet 6 I Filed NOV. l5, 1955' Piaf/VER Y" var A` @5 )wa/Wam M. R. FENsKE ET Al. 2,052,971

PROCESS FOR TREATING MINERAL OILS Filed Nov. 13, 1933 7 Sheets-Sheet '7 Sept. 1, 1936.

Patented Sept. 1, 1936 `,UNITED STATES PTENT OFFiCE Merrell R. Fenske and Wilbert B. McCluenState College, Pa., assignors vto Pennsylvania Petroleum IResearch Cor of Pennsylvania poration, a .corporation Application November 13, 1933, Serial No. $97,858v

1s claims'. (c1. 19e-ia) This invention pertains generally to the separation of materials of all kinds and pertains particularly to the solvent extraction and/or iractionation 'of mineral oils. It will be described 5 in connection with the solvent extraction and/or fractionation of lubricating oils. However, as above indicated, it may be employed for many other purposes.

While we appreciate that practically nothing is known concerning denite substancesA which comprise the complicated mixture known as mineral oil and still less is known concerning the compounds present in the heavier or lfractions except that the molecularweights of the molecules are large, which makes it possible to have varying types of structures existing in the same molecule, yet there is evidence which leads to the conception that the types of molecules in lubricating oils may be divided into perhaps three classes.

The molecules of these three classes are thought to have structures containing rings and chains and the following hypothetical classification is based, first, upon whether the rings are unsaturated or saturated, and second, upon the relative length of the chains attached to the rings.

The term chain implies either substantially a straight chain or a relatively highly branched chain.

The molecules of the first class are conceived to have rings which are appreciably unsaturated with chains attached to the rings but with the ring type of structure preponderating. By unsaturated we mean that it is possible to add hydrogen 35 to the compound without materially disrupting the hydrocarbon structure. Molecules of this class may be regarded as having asphaltic characteristics.

The molecules of the second class are conceived to have rings which are principally saturated, such as those of cyclopentane or cyclohexane, with a considerable number of chains attached thereto. The carbon atoms are thought to be about equally divided between the chains and the rings. 45 Molecules of this class may be regarded as having naphthenic characteristics.

The molecules of the third class are conceived to have rings which are predominately saturated and to have chains attached to these rings which 50 are relatively long and involvedk compared to the chains of the second class. The carbon atoms in the chains are thought to be materially in excess of those in the rings. This class of molecules may be regarded as having paramnic characteristics. It is to be understood, however, that the forelubricating oil f goingy thoughts relative to molecular arrangements are employed simply to portray the overall or average condition or the molecular species consituting an oil and that any one or more of such molecular arrangements may comprise petrot leums or oils according to the type.

For the purposes of simplicity in description, the first and second classes of molecules will be referred to herein as being of the ring type and the third class of molecules will be referredto 10 herein as being of the chain type.

By solvent extraction is meant the separation of a mixture into parts in which each part has a preponderance ofmolecules of a particular type. As applied to mineral oils and particularly lubricating oils, this generally means the separation of compounds of naphthenic and/or asphaltic characteristics from compounds having parafflnic characteristics.

By solvent fractionation is meant the separation of a mixture intoparts in which each part has a preponderance of molecules of a particular general size. It is comparable to fractionation by distillation as far as results are concerned in that, for instance, an overall or reduced crude may be fractioned into desired fractions such as gasoline, kerosene, gas oil, wax distillate, and cy1 inder stock, or wax distillate and cylinder stock as the case may be.

The above definitions are not intended to be all-inclusive or all-exclusive and are given merely for the purposes of illustrating the invention.

In solvent extraction the desideratum has been the separation of ring compounds regardless of molecular size from chain compounds regardless of molecular size and including the smaller molecules.

In soivent fractionation the desideratum has been the separation of molecules of one general size from molecules of another general size or sizes irrespective of whether such molecules are of the chain or ring types.

The selectivity of a solvent may be regarded as being its inherent ability to dissolve molecules of a type or size in preference to molecules of a diiierent type or size, as the case may be.

The efficiency with which a solvent operates in a particular process may be regarded as being a function of the process and of the chemical nature of the solvent.

As described and claimed in copending application Serial No. 10,932 filed March 13, 1935, we have found it very desirable and eicient to bring about the separation of materials either according to molecular size or type, or both by processing 'Iii the oil with solvents inia column where intimate contact of the various phases may take place by causing relative movement between said oil and solvent to take place in the presence of a group of attenuated packing members arranged side by side and longitudinally in the zone of contact. In some cases the solvent and oil may be processed countercurrently to one another, while in other cases they may be contacted when owing in the same direction. y

This later procedure is useful when solvents and oil are being contacted to obtain a certain amount of oil dissolved or precipitated.

For example, if we wished to dissolve a certain amount of oil, we might mix in a mechanical manner the oil and solvent in a tank until the proper degree of solution has occurred. Since it obviously requires time and contact of solvent and oil, we would have to mix or stir the materials either until equilibrium had been established for the amount of oil and solvent contained in the tank, or until the desired degree of solution occurred, if this degree of solution were less than the equilibrium concentrations. Instead of using mechanical devices, such as stirrers or agitators, we may bring about the same result by allowing the oil and solvent to flow in the same direction in a tower where packing', or plates or other contacting means is provided, and where the time required for any given quantity to flow through the tower is sufcient to effect the desired degree of solution. Operating in this Way, we avoid mechanical stirring, we obtain intimate contact so speeding up the solution processes, and we have a process very suitable for continuous operation.

In general, however, we nd countercurrent processing more desirable.

Again referring to thetank and mechanical stirring operation we might cool and/or add another solvent to the rst solvent-oil solution and/or vaporize a part of the solvent to effect precipitation of oil from solution. However, we prefer to use a tower in which intimate contact of the solution and precipitating medium occurs, and in the same way as in solution processes, we now precipitate oil to the desired extent in a continuous manner, without mechanical agitation.

The countercurrent processing of oil and solvents ls very desirable for in this way we obtain the equivalent of using a great many separate batches of oil and solvent, in one operation. If we analyze more fully extraction processes such as carried out in a tower using packing materials, or plates, and countercurrent flow of materials, we nd that such a process is much more efcient than any single batch operation, and the results of the tower may be analyzed in terms of a number of successive perfect extractions brought about by the countercurrent iiow of materlals, and intimate contacting of the same.

By a perfect extraction we mean one in which the equilibrium is rapidly and completely established between the various phases present using the minimum amount of materials. Also we consider in this case that the solvent should be of such a type as to exert the maximum solubilizing effect on one type or size of molecule and the minimum on the other or opposite type of component. All actual4 processes for carrying out extraction in a practical way never reach this ultimate goal, but approach it to varying degrees.

Likewise, through the proper application of precipitation effects, we have found that a much more eillclent practical operation is possible. This is accomplished by proper combination of precipitation and solution effects for the purpose of creating reflux in the tower.

By reflux We mean that a certain proportion of oil flows in a circulatory way between the top and bottom, or vice versa of the column. This circulatory flow is usually in different phases when flowing in opposite directions in the column. Certain proportions of the oil move in one direction in the solvent phase and in the opposite direction i-n the oil phase, and so is continually recycling itself. This we call reux. By processing our materials in this way with reflux we obtain the following results and advantages.

(1) The result is the equivalent to more nearly approaching the ideal perfect extraction mentioned earlier, or to having a longer column. These are practical and economic advantages.

(2) A higher yield of a given quality or a greaterquality of a given yield result than, when operating without reflux.

(3) The specificity of a given solvent is improved. Operating with reflux is equivalent to using a more selective solvent and no reilux. Thus we can select materials as solvents from a Wider class of substances or those available in greater quantity at lower initial cost and lower operating cost.

(4) Thus the resulting effects of processing with reiiux are to have the equivalent of improving the selective character of the solvent, to have the equivalent of increasing the efiiciency of contactdtgthe solvent and oil, to have the equivalent gf rising a longer column.

This invention pertains more particularly to the novel use of a plurality of columns for fractional precipitation purposes.

A further feature of this invention relates to a process and apparatus for increasing the eiliciency 0I solvents for extraction and/ or fractionation purposes.

A Iurther feature of this invention relates to a new and novel process for the solvent extraction and/or fractionation of materials.

A further feature of this invention relates to new and novel apparatus for the above purposes.

Further features of this invention reside in the construction, arrangement and combinations of parts, and in the steps, sequences and combinations of steps, all of which together with further features will become more apparent to persons skilled in the art as the specification proceeds and upon reference to the drawings in which like reference characters have been appended to like parts in the Various figures and in which Figure l is a sectional elevation of one type of column which may be employed in carrying out the invention;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 is a section on line 3-3 of Figure l;

Figure 4 is a flow sheet illustrating one manner of connecting -a plurality of columns for carrying out the invention;

Figure 5 is another ow sheet;

Figure 6 is a further ilow sheet;

Figure 7 is a still further flow sheet;

Figure 8 is a diagrammatic illustration of a diierent form of apparatus;

Figure 9 is a sectional elevation illustrating a number of diilerent modications; and

Figure l0 is a section on line l--lll of Figure 9.

In practicing the invention herein, a part or all of the material to ybe separated is initially dissolved in solvent. If a part only of the material without to be separated is dissolved, the residuum comprises one of the separated portions. A part or parts of the material dissolved in the solvent is then precipitated therefrom either in one step to obtain one portion or in a plurality of succeeding steps to obtain a plurality of portions.

In a specific form' of the invention the solution of the solvent and the material to be separated takes place byl parallel or countercurrent ow of the two substances through a column of the order described and claimed in said copending application Serial No. 10,932, and the precipitation likewise takes place in a column or columns of the same character, the precipitate being caused to iiow parallel or countercurrently to the solution in each of the precipitating columns.

A column of this type is illustrated at ID in Figures 1 to 3. Column I0 comprises a plurality of vertically arranged spaced tubes Il which are joined at opposite ends through the medium of plates I2 and I3 which may be of the order of headers. As illustrated, plates I2 and I3 are integral with flanges I4 and I5 between which is supported a shell I6 which surrounds tubes II to form a chamber I1 for heat exchange purposes, shell I6 being provided with openings I8 for the ingress and egress of a heat exchange fluid such as steam, water, or brine.

Flange I4 is shown connected to a flange 20 of segregating chamber 2l and flange 22 on segregating chamber 2| is shown connected to a flange 23 on feeding chamber 24.

Feeding chamber 24 is separated from segregating chamber 2l by means of a partition 25 which has a plurality of apertures 26 of the same number as the tubes II. Each aperture 26 has secured therein a feeding tube 21. Each feeding tube 21 extends down into a separate tube II.

Chamber ZI has an outlet 29 which is illustrated as being controlled by a valve 30. Chamber 24 has an inlet 3i which is illustrated as being controlled by a valve 32.

Flange I5 is illustrated as being connected to flangel 33 on feeding and segregating chamber 34. Chamber 34 has an inlet 35 illustrated as being controlled by a valve 36 and an outlet 31 illustrated as being controlled by a valve 38.

Each of the tubes II is shown packed with a packing 39. Packing 39 may be of any desired type employed in distillation or fractionation processes, for instance, such as jack chain. However, packings which are found to be extremely emcient are more particularly described and l claimed in copending application, Serial No. 677,755 filed June 26, turn, double turn, triple turn, or polyturn helixes, open rings, H-shaped, S-shaped, #-shaped wire forms, ordinary carding teeth such as used in the textile industry, bent carding teeth, and similar forms. The dimensions of the various forms are generally comparable to those of carding teeth, although other sizes may be employed depending upon the results desired.

The tubes II may have a cross section of any desired geometrical configuration and within certain limits of any desired area. The cro-ss section of each tube I I is preferably limited to an area sufficiently small to prevent serious channeling after any contacting means, for instance packing, has been arranged' therein.

The preferred limiting cross sectional area for each tube II will be not only a function of the type of contacting means employed, since the small wire forms speciiically described herein will as a rule permit the use of a larger cross section 1933, and comprise single than raschig rings or jack chain, but also of the manner in which the contacting means is arranged in each tube, for instance, of the degree of uniformity of distribution of packing. Since thetubes may have sides which are straight or indented or of other surface configuration, the departure of a tube from a straight or continuous form will have its influence. For this reason a definite limit in cross sectional area which, if exceeded in size, will no longer demonstrate the substantial increase in eiiiciency which we have discovered results from a constriction of cross sectional area, cannot be given but may be read ily determined, for instance by testing the efciency of single tubes of different sizes after any contacting means to be employed has been arranged therein.

It may be stated as a general rule that one should proceed with caution after exceeding a cross sectional area equivalent to that of. a circulartube in the neighborhood of two or three inches in diameter, although, with the proper selection of packing or other contacting means anda careful distribution in each tube, it is pos sible that larger cross sectional areas may be employed while in other cases smaller cross sectional areas may be required. Therefore, the term relatively small cross sectional area or its equivalent, when employed y'in this specification and in the claims, is intended to mean a cross section which, when taken in'conan inordinate falling oil" of eiciency junction with any contacting means, is sufficiently 4 small to materially increase the contacting eiiiciency because of the constriction of its area.

We have obtained highly eicientliquid phase contact in metallic tubes of various cross sectional y' areas, for instance tubes of circular cross.sec tion and of 3@ inch, of l inch and of 1.5 inches in diameter. l'

If tubes 21 are of substantially equal diameter and length, the heavier chamber 24 will in turn be fed into tubes II substantially equally. Any other construction might be provided for this purpose.

1f tubes II are of substantially equal diameter the lighter liquid which is fed intoich'am-y ber a4 will in tum be fed im@ tubes H substerl-lf tially equally. Any other construction may also be provided for this purpose.

As described and claimed in copending application Serial No. 10,932, when the column of Figures 1 to 3 inclusive is employed to effect partial or total solution between a solvent and a mineral oil, the heavier liquid usually enters the column through chamber 24 and is feddown into tubes li through tubes 21. The lighter liquid is usually fed in through opening 35 and flows upwardly through tubes II countercurrently to the down flowing heavier liquid due to the dilTerence-in their densities. As a general rule, the lighter liquid dissolves a part of the heavier liquid to form a light solution which is withdrawn from the column at 29 and the heavier liquid ,dissolves a part of the lighter liquid to form a heavy solution which is withdrawn at 31. 1f one liquid completely dissolves the other of course only one solution is formed.

In orderto facilitate the countercurrent flow a layer of the heavier solution may be maintained in chamber 31 at a more or less constant height.

As the two liquids pass each otherthrough the tubes II they, are brought into intimate contact over a very large surface area. This contact is liquid which is fed. into greatly improved when the more efficient types of packing such as those above set forth are employed. Both liquids are caused to spread out over a very large surface area compared with their volumes and at least one of the liquids will ordinarily 'be caused to alternately form films and drops, the drops detaching themselves from thepacking and flowing through space to recontact the packing and spread out into lms again. This brings a relatively large percentage of the liquid particles to the surface for contact with the other liquid. k The oil will generally pass through the column in this manner.

If tubes Il are of substantially equal diameter and packed in the same manner, and ii.' the two liquids are fed into the tubes Il substantially uniformly by any suitable means such, for instance, Aas that disclosed, substantially the same conditions will obtain in each of the tubes Il. If the tubes Il are of relatively small diameter, serious channeling of the liquids may be avoided.

Since the result of having tubes Il of substantially the same size 'and of substantially equally dividing each feed liquid among the tubes l; l is to maintain substantially the same proporl tion of solvent phase to oil phase in each tube, it will be obvious that tubes H may be of different sizes and that the feeding rates may vvary accordingly, particularly if substantially the same proportion of phases is maintained in each tube.

In other words, the result of having tubes Il of the same size and of maintaining uniform feeding conditions in each tube, is to cause the Aaiiinate phase produced by each tube to be of substantially the same composition as the railinate phase produced by any other tube; and to cause the extract phase produced by any tube to be of substantially "the same composition as he extract phase produced by any other tube. From this it will be obvious that if tubes Il should vary in size the feeding rates may be adjusted to obtain similar conditions.

Tubes Il may be of any number. The number of tubes employed will depend upon the desired throughput of the column.

It is, of course, to be understood that other columns may be employed, and that the liquids may iiow in parallel rather than countercurrently as previously referred to.

The column may be operated at any desired temperature by the use of a heat exchange medium in chamber I1, and at any desired pressure, whether it is atmospheric, sub-atmospheric, or super-atmospheric.

In the case of countercurrent flow, if the oil is heayierthan the solvent, it will of course be fed into the column through chamber 24 and any undissolved part, or, in other words, the oilsolvent solution will be withdrawn through outlet 31. The solvent will be fed into chamber lll through opening 35 and the undissolved porther words, the solvent-oil soluithdrawn through outlet 29.

If the oilV is lighter than the solvent, it will be fed into the column through opening 35 and tbc oil-solvent solution will be withdrawn at t9. Thesolvent will be fed into the column rough 24 and the solvent-oil solution will be withdrawn at 31.

As described and claimed in copending application Serial No. 10,932 to employ the column for precipitation purposes and to cause reflux of a part of the oil, the solvent-oil solution may be fed into the column either through inlet 3| or through inlet 35 depending on Whether the oil (or, strictly speaking, oil-solvent solution) to be precipitated is lighter or heavier than the solution. Since the solvent-oil solution is spread out into thin films on the packing the precipitation has an excellent opportunity to be selective. If the precipitate is heavier than the solvent-oil solution, the solvent-oil solution may be fed in at 35 so that the precipitate may flow countercurrently to the solution. If the precipitate is lighter than the solution, the solventoil solution may be fed in through inlet 3| so that the precipitate in this case may also flow countercurrently to the solvent-oil solution. By this means the precipitate is thoroughly scrubbed by the eiicient contact previously referred to.

Precipitation may be brought about by cooling the solution as lt passes through the tubes Il. Since the solution is spread out substantially uniformly over the packing in thin films, excellent conditions are present for rapid, effective Aand uniform heat transfer and consequently rapid, uniform and selective precipitation. lWhen. the precipitate is heavier than the solvent-oil solution, it flows downwardly and countercurrently thereto, is segregated from said solution in chamber 34, and is Withdrawn through outlet 31. When the, precipitate is lighter than the solventoil solution, it flows upwardly and countercurrently to said solution and is withdrawn at 29. Precipitation may also be brought about by the addition of a third liquid, for instance,` one solvent but a relatively low miscibility with the which has a relatively high miscibility with the oil. When the solvent is pyridine, for instance, .such a liquid is methylcellosolve. Reference is made to copending application Serial No. 704,052 flied December 26, 1933. The precipitating liquid may be introduced into the column along with the solvent-oil solution when its density is such that it tends to ilow in the same direction as said solution until dissolved. On th'e other hand, when'the density of the third liquid is such that it tends to flow in an oppositeY direction to the solvent-oil solution until dissolved, it may be introduced at the opposite end of the column so that the countercurrent iiow may be availed the solvent. Or the third liquid may be'introduced into the column at any desired point intermediate the ends thereof. The latter is pre- ,ferred in the case where the precipitant tends to ow in parallel with the solvent-oil solution so as to assure precipitation within the column itself for reflux purposes.

The column may also be employed for strip, ping a part of the solvent from the solvent-oil solution to concentrate said solution (either with or without super-saturating the same to cause precipitation). The solution, regardless of the relative density of the precipitate, may be fed in through inlet 3| and allowed to trickle down over the packing and thus ow countercurrently to the upflowing vapors. The column may be maintained at any desired temperature and absolute pressure to cause the desired quantity of the solvent to change from the liquid to the vapor phase. The column is again an excellent medium for heat transfer. It is also an excellent medium for efficient vaporization.

Thus precipitation of oil from the solvent-oil solution may be brought about in any one of three ways: to Wit, by reduction in temperature, by reduction in solvent content, or by the addition of a precipitant. Two or more of these precipitating methodsmay' ybe combined.v We have, therefore, several ways in which precipiutationmay be broughtabout, of which the Iolllowing` table is an example.

There are several ways in which the forego-l 15 ing methods of precipitating the oil may be employed. One manner comprises first dissolving allor a substantial part of the oil and then precipitating desired percentages of the oil in steps, removing the precipitate in each step before pro- 20 ceeding rwith tlie next step. For instance, if it is desired to divide the oil into ten equal parts (either for separation `as to molecular type or as to molecular size) either 100 per cent or 90 per cent of the' oil might be dissolved. Ii 10G per 25 cent of the original oil were dissolved, nine seplso arate precipitations of oil might be made, each precipitate comprising substantially per cent` of the original oil. This would leave 10 per cent of the original oil still dissolved in the solvent from which it might be recovered, for instance,

by` distillation. If 90 per cent of the original` oil were dissolved, 'eight separate precipitations of the oil might be made. The undissolved oil would comprise the rst cut. The precipitates would comprise the second, third, fourth, fifth, lsixth, seventh, eighth, and ninth cuts in their or- `der and the :tenth cut would remain dissolved in the solvent, from which it might be recovered in any desired manner.

The ten cuts in either case would vary either as Vto molecular type or as to molecular size, depending, of course, on the solvent employed,

'Examples of .solvents which are substantially selective as to molecular type are pyridine, ace- 4" tone, beta-beta-dichlorethyl-ether, sulfur dioxide, and `nitrobentene; and examples of rsolvents which are `substantially selective as to molecular size are certain monohydric aliphatic alcohols'.v Referenceis here made to copending application so Serial No, 731,778 sied June 21, 1934.

"" any precipitant or combination of precipitants m precipitation. For instance, in Figure 4`is shown a plurality of columns of the orderof `the columns may be employed. s

In accordance with this invention, the columns may be combined in any desired manner for the purposes of eecting precipitation or solution and of Figures 1 to 3 arranged in av continuous ilow system for the purpose of illustration. Six col- Vurnns, 40, l4I, 42, 43. 44, and 45 are illustrated.

" However, any desired'number may be employed.

These columns are illustrated as being connected in series and the arrangement is more particularly adapted for use when the original oil and all of the precipitates are heavier `than the solvent or the solvent-oil solution at any stage of the precipitation. Columns 48 to 45 have inlets 46, 41, 48, 49, 58, and 5| respectively for lighter liquid and inlets 52. 53, 54, 55, 56, and 51 respectively for heavier liquid. Columns 48 to 45 inclusive have outlets '58, 59, 60, 6|, 62, and 63 for lighter solution and outlets 64,65, `68, 61, 68,v and69 for heavier solution.

Outlets r64 to 69 lead to receivers 10, 1|, 12, 13,

14, and respectively, the flowv being controlled by valves illustrated at 16, 11, 18, 19, 80, and`8| respectively.

' Outlet 58 is connected to inlet 41 through a. head regulator or pump 82. Outlet 59 is connected to inlet 48 through a head regulator 83. Outlet 60 is connected to inlet 49 through a head regulator 84. Outlet 6| is connected to inlet 50 through head regulator 85. Outlet 62 is connected to inlet 5|,through head regulator 86. Outlet 63 leads to a receiver 81. l

The arrangement of Figure 4 may operate as,`

follows:

Oil enters column 40 through inlet 52; solvent enters column 40 through inlet 46; the solventoil solution leaves column 40 through outlet 58;

v and the oil-solvent solution, if any, leaves column -40 through outlet 64.

Column 40 is thus employed for effecting solui tion between oil and solvent to obtain the solventoil solution for subsequent precipitation purposes.

As the solution `passes up through column 4| veither its temperature may be reduced to throw oil out of solution or a precipitant may beadded for this purpose, or both may be employed. The precipitated oil (or more correctly, oil-solvent solution) flows countercurrently to the upilowing solution, collects at the bottom of column 4|, isy

'The solvent-oill solution leaves column 4| atl 59 and enters column 42 at 48, wherein further precipitation-may take place either by temperature reduction or by the addition oi a precipitan't or both, and the precipitate is collectedin recelver`12.

The solvent-oil solution leaving column 43 at 6| enters column 44 at350and further precipitation may take place in column 44, the precipitate being collected in receiver 14.

The solvent-oil solution 'leaves column 44 at `62 and enters column 45 at 5| wherein further precipitation may take place, the precipitate being collected in receiver 15. The spent solvent-oil solution leaves column 45 at 63 and is collected in receiver 81.

` 'Ihe arrangement shown in Figure 5 is particularly adapted :for use when the solvent is heavier than the oil and all of the the precipitates are lighter than the solvent-oil solution.

In this case the undissolved eiland the precipitates rise to the top of columns. Therefore, outlets 58, 59, 60, 6|, 62, and 63 lead to receivers 10, 1|, 12, 13, 14, and 15 respectively. Outlet 64 is now connected to inlet53 through pump 82; outlet 65 is connected to inlet 54 through pump 83; outlet 6B is connected to inlet 55 through pump 84; outlet 61 is connected to inlet 56 through pump 85; outlet 68 is connected to inlet 51 through pump 86, and outlet 69 leads to receiver 81.

In operation solvent enters column 4l! through 52 and oil through 46. In this case the oil tlows til the precipitate becomes heavier than the solupwardly and the solvent downwardly and any undissolved oil (oil-solvent solution) is collected in receiver 10. The solvent-oil solution is segregated from the inilowing fresh oil at the bottom of column 40 and is pumped to the top of column 4l wherein as in columns 42, 43, 44, and 45 precipitation may take place either by temperature reduction or by the addition of a precipitant or both, the precipitate in each case being collected in receivers 1i, 12, 13, 14, and 15 respectively.

As in the previous case, if the precipitant tends to flow along with the solvent-oil solution rather than countercurrently thereto, it may be fed along with said solution into columns 4| to 45, for instance, through pumps 82 to 86 respectively, but preferably at an intermediate point in the column as previously pointed out. On the other hand, if the precipitant tends to flow countercurrently to the solvent-oil solution until dissolved, it may be fed into columns 4I to 45 through inlets 41 to 5| respectively. Even if the precipitant flows along with the solvent-oil solution, it seems preferable to introduce the precipitant at some point mid-way between the two ends.

Cases may arise, particularly when the density of the solvent is close to that of the oil, in which, during solution of the oil and solvent and during the initial or first few precipitating steps, the oil and precipitates will be heavier than the solvent and solvent-oil solution respectively, but after one or more precipitations have taken place the precipitate may become lighter than the solvent-oil solution.

This might occur in solvent fractionation since the precipitates become lighter and lighter in density as the 'precipitation proceeds. For instance, in the solvent fractionation of a crude, the fractions or precipitates comparable to cylinder stock and wax distillate might be heavier than the solvent-oil solution, whereas fractions or precipitates comparable to gas oil and kerosene might be lighter than the solvent-oil solution. The former precipitates would settle to the bottoms of the columns whereas the latter would rise to the tops. l

It, therefore, becomes desirable to feed the solvent-oil solution at the bottoms of the precipitating columns until the density of the precipitates becomes less than that of the solvent-oil solution and then feed said solution at the tops of the precipitating columns until the desired precipitation is completed.

A column hook-up for this purpose is illustrated in Figure 6.l In Figure 6 columns 40, 4i, 42, and 43 are connected'in the same manner as shown in Figure 4, whereas columns 44 and 45 are connected as illustrated in Figure 5. Outlet 6I of column 43 is connected to inlet 56 of column 44' through the head regulator 85. 'Ihe operation of the equipment will be obvious from the previous description.

It is also possible to have cases in which the original oil lis lighter than the original solvent and the first or first few precipitates are lighter than the solvent-oil solution, but in which the remaining precipitates are heavier than the solu; tion. In such cases the oil will be fed at the bottom of column 40 and the solvent at the top. The solvent-oil solution will be fed at the top or tops of the precipitating column or columns unvent-oil solution, whereupon the solution will be fed at the bottom or bottoms of the column or columns.

This might occur, for instance, in the solvent extraction of a lubricating oil when the density of the solvent is close to that of the oil, and particularly when the oil contains a relatively large quantity of ring compounds. Ring compounds are generally of higher density than the chain compounds. Assuming the original oil to be lighter than the solvent, it will be fed into column 40 at the bottom and the solvent will be fed into column 40 at the top. 'I'he first or first few precipitates will be predominately of the chain type and will rise from the solvent-oil solution which is fed at the top or tops of the first or first few precipitating columns. Then as the precipitates become predominately of the ring type their densities will become such that they will settle in the solvent-oil solution which is now fed at the bottom or bottoms of the remaining precipitating column or columns.

'I'his is illustrated in Figure 7 in which columns 40, 4| 42,v and 43 are connected as illustrated in Figure 5 and columns 44 and 45 are connected as illustrated in Figure 4. In this case outlet 8l of column 43 is connected to inlet l0 of column 44. Otherwise the connections are as previously described.

The operation of the hook-up illustrated in Figure 7 will be obvious from the previous description.

It should be noted that in Figures 6 and 7 the same provision is made for the addition of precipitant which might, however, be added at intermediate points on the columns as will hereinafter appear.

It will be seen that the apparatus of Figures 4 to 7 is suitable for the first, third and fifth precipitating methods above outlined. Each of the second, fourth, sixth, and seventh precipitating methods call for the reduction of the solvent content in the solvent-oil solution.

The reduction in solvent content may be effected by vaporization. Vaporization-may be suitably brought about in a column, particularly when the latter is of the packed type, or by any other suitable means, for instance, a flashing coil.

Precipitating method No. 2 calls merely for the reduction in solvent content. This may be brought about in a column through the application of heat to the solvent-oil solution, the vapor being removedv as previously described. Any number of columns may be connected in a series, the solution being segregated from the precipitate at the bottom of one column before its introduction into the next. This separation may take place by allowing the liquids to settle or by means to be hereinafter described. The vapor may be condensed and collected in a receiver in the usual way.

Precipitating method No. 4 calls for both the reduction of temperature and of solvent content. 'Y

This may be accomplished by reducing the pressure on the solution and thus permitting the solvent to vaporlze due to the reduced absolute pressure rather than by the application of heat. 'I'he latent heat absorbed from the solution during the vaporization will reduce its temperature and will assist the precipitation caused by reduction in solvent content. The temperature might be otherwise reduced.

Precipitating method No. 6 calls for no reduction in temperature but for the reduction in solvent content and for the addition of a precipitant. The reduction in solvent content might take place in a column, for instance, with the application of heat, and the precipltant might be pumped into the column along with the solution, or otherwise.

Precipitating methodv No. 7-cal1s for a reduction-in temperature, a reduction in solvent content, and the addition of a precipitant. lA reduction in temperature and solvent content might be effected by reducing lthe absolute pressure as previously described and the precipitant might be'added yto the solution as it passes into' the column, or otherwise.

It is, of course, possible to insert vaporizing columns or other suitable means such as flashing coils between any two of the columns shown in Figures 4, 5, 6, and 7, for instance. for the purpose of concentrating the solution at a higher temperature so that further precipitation may be brought about by cooling Without the necessity of resorting to refrigeration which is relatively more costly. The solution may or may not be supersaturated in the vaporizing column to cause precipitation as desired.

This is illustrated in Figure 8 in which the columns of Figure 4 have been arranged so that column 43 becomes a vaporizer. In order tocause the solution to trickle downwardly through the column countercurrently to the up-iowing vapor, outlet 60 of column 42 is shown connected to inlet 55 of column 43. However, the solution may be introduced into column 43 at an intermediate polnt and this may be preferred in many instances. Outlet 5| of column 43 becomes a vapor outlet. 'Ihe vapor is illustrated as being conducted into a condenser 92 where it is condensed and the condensate is collected in receiver 93.

Outlet 31 of column 43 as illustrated leads to .the vertical center of a settling tank 94 in which the precipitate settles to the bottom since in Figure 4 the precipitate is presumed to be heavier than the solventoil solution. If no precipitation takes place in column 43, outlet 61 may be connected directly to inlet 50 of column 44, other wise outlet 95 at the top of the tank 94 'may be connected to inlet 50 through the head regulator 85. 'Precipitated oil is removed from tank 94 through outlet 96 at the bottom thereof and is collected in a receiver 91.

If the vaporizer. were connected in an arrangement such as illustrated in Figure 5 in which the precipitate is lighter than the solventoil solu tion, outlet 6l would be directly connected through inlet 56 of the next column if no precipitation took place in the vaporizer or through settling tank 94 if precipitation took place. In the latter case outlet 96 of tank 94 would be connecd to inlet 56 of column 44 and outlet 95 of tank 94 would be connected to receiver 91.

Since the'vaporizlng column may be operated at reduced pressures, a vacuum pump 98 has been illustrated as being connected to receivers 93 and 91 and tank 94.

Any other separating means may be employed at the bottom of the vaporizing column, such. for instance, as a centrifuge.

When precipitants are used in connection with vaporizlng steps, if it is not desired to reduce the concentration of precipitant, it will be obvious that it should be of a higher boiling point than the solvent. Furthermore, since fractionation will be necessary in many cases, the solution will preferably be introduced into the column at an intermediate point.

Any precipitant may be used in any of the foregoing methods regardless of its non-solubility, solubility, or degree of solubility in the oil,

If the solvent were one which is selective as to type of molecule, it would dissolve ring com- .pounds out of the added oil and dissolved chain compounds would be precipitated from the solvent. Any ring compounds in the added oil would go into solution with the solvent in preference to any dissolved chain compounds. In other words, ring' compounds would be scrubbed or stripped from the added oil and chain compounds would be scrubbed or stripped from the solvent.

This oil might be fresh oil and/or a part (or all) of the oil from the receiver connected to any one column might be fed back as a precipitant into a preceding column, for instance, the next preceding column. For example, a part (or all) of the oil from each receiver (except `the first since there is no preceding column) might be fed back as a precipitant into the next preceding coiumn in each case and/or fresh oil lmight be fed into any of the columns, for instance, the last one. An overall oil or any out or fraction thereof might likewise be used as a precipitant in the event that the solvent is seiective'as to size of` molecule. The more soluble portions of the added e oil would be dissolved out and would go into solution in preference to dissolved cil portions of a lesser solubility in the solvent. By regulating the amount of oil added in each column, a step by step precipitation might be effected for obtaining oilsof different viscosities and/or oil might be fed back from the precipitated oil receivers as previously pointed out.

The cuts or fractions might be employed in various other ways. and many other types and methods of operation will suggest themselves tov 'chamber |05, and a feeding chamber |06. Chambers |02 and |03 are similar to chamber 24 and 2| respectively (see Figure 1) except that in chamber |03 vertically spaced outlets |01 and |08 have been substituted for outlet 29. Tubes |04 are similar to tubes except that the tubes |04 have ends |09 which extend upwardly into chamber |03 to a point substantially midway between openings |01 and |00 and have ends ||0 which extend downwardly into chamber |05 to a point substantially midway between spaced outlets and ||2 thereof. Chambers |05 and |06 are substantially duplicates of chambers |03 and |02 respectively, the former corresponding to the inversion of the latter.

The purpose of providing spaced openings |01 and |08 in chamber |03 and spaced openings I|| and ||2 in chamber |05 is to adapt chambers |03 and |05 for the separation of two non-miscible liquids ofy different densities. For instance. either chamber |03 or |05 might be employed for the purpose of separating any undissolved precipitant from the solution or when`the column is used for vaporizationl purposes vchamber |05 might be employed to separate precipitant from solution.

Since the packing is employ-ed in many instances not only as a contacting means but also for heat transfer purposes, packing ||4 may be placed around the outside of tubes |04 for direct contact with the heat exchange fluid and for conducting heat to or from tubes |04. Packing 4 may be similar to packing ||5 on the inside of tubes |04.

The packing material is very effective as a heat exchange medium in view of the large surface area for the transferof heat. This is particularly true when the packing elements are joined together and/or to the tube walls. This eliminates surface lms between the packing elements themselves and between the packing elements and the tube walls and thus greatly increases the rate of heat conduction through the mass. This applies to the packing litiv whether or not packing ||4 is also employed.

Thepacking elements may be joined together and to the tube walls by any suitable means, for instance, by putting the packing ||5 and/or ||4 in place and thenraising the temperature to the fusionpoint of the material, preferably without ouslyvv melting dwn the packing. This is a1applicable particularly when the.y packing elements and the tubes are of glass.

When the tubes |04 and the packing ||5 and/or ||4 are of metal. the tubes |04 may be coated on the inside and/or outside with a metal or alloy of lower melting point. The packing elements may be made from a stock which has been previously coated with a metal or alloy of lower melting point. After the packing is in place, the temperature is raised to the fusion point of the low melting metal or alloy and the contacting surfaces may thus be joined.

Another mannerupf joining the mass into a single whole is to ilw a fused metal (or alloy) through the packing elements after they are in place. The amountfof metal (or alloy) deposited will be a function of its viscosity which in turn will be a function of its' temperature. Since a relatively high percentage of f ree space is generally desired, only a relatively small iilm of the metal should generally be deposited. The deposited metal (or alloy) will join all contacting surfaces which are wetted thereby.

Any desired metal or alloy may be employed for joining the packing elements together and to the tube walls. Examples of metals and alloys of lower melting point are ti zinc, cadmium, lead, soft solder, hard solder, type metal, bearing metal, etc.

It is possible to vary the temperature along the column should this be desired for any purpose, for instance, to regulate the rate of precipitation at points along the column. Shell IB which surrounds tubes |04 is shown divided into a plurality of segregated sections I1 for this purpose. Each section is provided with openings ||8 for the ingress and egress of a heat exchange fluid.

.It may be desired in many instances to introduce the precipitating liquid directly into the tubes |04 at an intermediate point, particularly in cases in which the precipitating liquid tends to ow in the same direction as the solution until dissolved as previously referred to. or in cases in which the direction oi.' travel of the precipitant is doubtful. It will also be preferred in many instances to introduce solution intol the ,column cent the bottom, or a plurality of means 1| I9 mayv be installed if desired.

For instance, by employing a plurality of means 9 at spaced points along the column, it is possible to vary the concentration of precipitant along the column.

Another means for introducing a liquid or liquids at any desired point or points intermediate the length of the column may -be had by extending tubes 21 and/or 21a into the column to any desired'point or points.

In the more specific embodiments of themvention heretofore more particularlydescribed,v

the solution enters each of the columns 4|, 42, 43, 44, and in a substantially saturated condition and reux is obtained by the more soluble portions of the precipitate going into solution with the solvent flowing countercurrently-ther'eto inpreference to less soluble dissolved/constituents which are thus caused. to come out-of .solution with the solvent.

If desired, the quantity of reiluxing oil may be increased by increasing the solvent power of the solvent of the solvent-oil solution afteritvleaves one column and before, as, or j ust after it-enters the next column. Since the solvent-oil solution is thus brought to an unsaturated condition more of the countercurrently flowing precipitate will be dissolved, and if We assume, for instance, that the same quantity of oil is thrown out of solution in the column, it will be obvious that the quantity -of material which circulates round and round in the column will be increased.

Any desired means may be employed for bringing the solvent-oil solution to an unsaturated condition after it leaves each column. Foxinstance the temperature of the solvent-oil solution might be raised, and/or additional solvent might be added, and/or the concentration of precipitant might be reduced such as by distillation, particularly if the precipitant has a lower boiling point than the solvent. A vaporizer, for instance, such as herein more specifically described might be inserted between any two columns for the lat-4 ter purpose if desired.

Any of the previously described means for bringing the solvent-oil solution to a4 supersatuf rated condition as it iiows through the column may be employed to cause the desired precipitation of oil in the column.

The temperature of the solvent-oil solution might be raised by any suitable means, such, for instance, as inserting a heating means in the path of the solvent-oil solution intermediate each pair of columns and/or the feeding chamber for the solvent-oil solution of the respective column might be jacketed for a heating fluid and/or the latter chamber might be provided with a heating coil and/or one or more of the heating sectionsv I1 (see Figure 9) adjacent the entry of solvent into the column might be employed.

If the solvent power of the solvent in the soltion of solvent ow, adding a preclpitant and/or vent-oil solution is to be increased by increasing the concentration of solvent, the additional solvent might be added at any suitable point, for instance. at the head regulators or yby any of the means provided at thesolvent-oil solution feeding end of the column `(see, for instance, Figure 9) which was previously described as being used ior the'addition of precipitant.

Means for the reduction of the concentration of precipitant has been previously referred to.

Many other variations will suggest themselves to persons skilled in the art upon becoming familiar herewith.

While the invention has been described in con nection with the initial solution of solventr and oil in the column 40, this initial solution may be ef- Iected by other means prior to the precipitation step or steps. The use of the column 40 makes itpossible to have a continuous iiow of all of the liquids which enter into the process, thereby making the system of the continuous rather than of the batch type. However, the process may be adapted to batch methods should this be desired for any reason.

The process and apparatus lend themselves suitably to the use of elevated pressures, for instance, for the purpose of maintaining in the liquid phase (wholly or partially, as desired) solvents whichare normally in the vapor phase at atmospheric pressure, and also lend themselves, suitably to reduced pressures, for instance, when a column is used as a vaporizer to return a desired portion of the solvent or solvents to the vapor phase.

While the invention has been described in connection with the countercurrent flow of the precipitate relativeto the'solution, a certain degree of efiiciency may through the column in the same direction, whether precipitation is caused by reduction in temperature, the addition of a precipitant, and/or by vaporization of a portion of the solvent. It should be noted that when any of the co1-` umns particularly described is employed in a manner to obtain a countercurrent iiow o'i uids, for instance, a countercurrent flow of precipitate and solution or the countercurrent iiow of solution and vapor, a substantialydegree of channeling is avoided the same as when the column is ern-` ployed for solution purposes. The same is also true when there is a parallel flow. It is also to be noted that substantially the same conditions will exist in each tube Il.

The columns may be arranged in any desired manner and any number may be employed, whether for solution, temperature reduction, precipitant addition, and/or solvent vaporization purposes.

While the columns will generally be larranged vertically, they may belinclined and, for instance, if used solely for heat exchange purposes, may even be horizontal.

Catch-al1 facilities may be provided in the `upper segregating chamber for separating entrained liquid desired. y

When a column is used as a vaporizer, any desired portion of the condensate may be reiluxed from the vapor if necessary or or reux may be caused by reducing the operating temperature of the column in the direction of vapor flow. Likewise, reilux may be caused in a column,` usedi'or solution purposes by reducing be obtained when both flow reducing the solvent concentration, as described and claimed in copending application, Serial No. 10,932.

It will, of course, be understood that sight gauges or any other means, may be provided on any or all of the feeding and segregating chambers of the variouscolumns in order that the dividing plane between any'- two liquid layers may be ascertained. v

\ While embodimentsA ofthe invention have been particularly described for the purposes of illustration, itis to be understood that changes, omissions, additions, substitutions and modications other than those specically mentioned may be made without departing from the spirit thereof. The claims,` therefore, are intended to be limited Aonly as required by the prior art.

We claim:

y 1. A process for fractionally precipitating a material such as mineral oilfrom a solution thereof in a suitable solvent, comprising flowing said solutionserially through a plurality of columns, each column having a plurality of phase contacting paths of'relatively small cross 'sectional 1,7 area connected in parallel, causing precipitation of said material in the paths of said columns, iiowing the precipitates in said paths countercurrently to thesolution therein, separating said precipitates, and feeding a portion of the pre-,f

cipitate separated from each succeeding column back into the column preceding it in a manner so that said precipitate will iiow counter-currently to the solution in said preceding column.

2. A process for fractionally precipitating a material such as mineral oil from a solution thereof ln a suitable solvent, comprising flowing said solution serially through a plurality'oi columns, eachcolumn having a plurality of phase contacting paths of relatively small cross sectional area, causing precipitation of said material in the paths of said columns, ilowing the precipitate in the paths 'of said columns counter-currently to the solution therein, separating said precipitates from said columns, feeding a portion of the precipitate separated from one column back into the next preceding column in a manner so that said precipitate will flow-counter-currently to the solution in the paths of said preceding column, and maintaining the ratio of precipitate to solution at least substantially the same in the paths of any one column.

3. A process for precipitating a material such as mineral oil from solution in a selective solvent comprising, flowing said solution serially through a plurality of columns each having a plurality of phase contacting paths of relatively small cross sectional area connected in parallel, precipitating a part oi said material from solution in said solvent in the phase contacting paths of each column, and causing the precipitate ineach column to flow countercurrently to the solution passing therethrough. Y

4. In a process for precipitating a material such as mineral oil from solution in a selective solvent, said material. being of greater density than said solution, comprising owing Said solution serially through a plurality of columns each having a plurality of phasecontacting paths of relatively small cross sectional area connected in t the solvent power of the solvent in the direction f of solvent flow, for instance, by reducing the ,Y columns whereby said precipitate flows counter- 75 operating temperature of the column in the direccurrently to said solution view of the difference 75 in density and segregating precipitate adjacent the base of each column.

5. In a process for precipitating a material such as mineral oil from solution in a selective solvent, said material being lighter than said solution, comprising flowing said solution serially through a plurality of columns each having a plurality of phase contacting paths of relatively small cross sectional area connected in parallel, said solution owing downwardly through each column, precipitating a part of said material from solution in said solvent in each column whereby said precipitate flows countercurrently to said solution, and segregating precipitate adjacent the top of each column.

6. A process for fractionally precipitating a material such as mineral oil from solution in a selective solvent, one portion of said precipitate being heavier than said solution and another portion of said precipitate being lighter than said solution, comprising owing said solution serially through a plurality of columns each having a plurality of phase contacting paths of relatively small cross sectional area. connected in parallel, precipitating a portion of said material in each of said columns, flowing the solution upwardly through those columns in which the precipitate is heavier than the solution, and flowing the solution downwardly through those columns in which the precipitate is lighter than said solution whereby each portion of said precipitate is caused to ilow countercurrently to said solution.

'1. A process for precipitating a material such as mineral oil from solution ina selective solvent, comprising owing said solution serially through a plurality of columns each having phase contacting paths of relatively small cross sectional, area connected in parallel, causing precipitation of said material in said columns by reducing the temperature of said solution, and concentrating said solution at a higher temperature with the removal of solvent intermediate said columns to lessen the total range in temperature reduction required to precipitate a given total amount of material.

8. A process comprising at least'substantially saturating a selective solvent with mineral oil by countercurrently iiowing said solvent and oil through a column having a plurality of phase contacting paths of relatively small cross sectional area connected in parallel, flowing the solutlon thus produced through a second column having a plurality of phase contacting paths of relatively small cross sectional area connected in parallel, precipitating a part of the dissolved oil in said second mentioned column, and flowing said precipitate through said second mentioned column countercurrently to said solution.

9. A process for fractionally precipitating a material such as mineral oil from a solution thereof in a selective solvent comprising, flowing said solution serially through a plurality of columns each having a plurality of phase contacting paths of relatively small cross sectional area connected in parallel, causing precipitation of said material in each of said columns, flowing the precipitates in said columns countercurrently to the solution therein, and increasing the solvent power of the solvent in said solution to bring said solution to an unsaturated condition after said solution leaves afpreceding column and before said solution is brought to a supersaturated condition to cause precipitation in the next succeeding column.

10. A process for precipitating a material such as mineral oil from solution in a selective solvent comprising.' flowing said solution serially throughl a plurality of columns each having a plurality of phase contacting paths of relatively small cross sectional area connected Yin parallel, and precipitating a part of said material from solution in said solvent in the phase contacting paths of each column. f

11. A process for precipitating a material such asv mineral oil from solution in a suitable solvent comprising, flowing said solution serially through a plurality of columns each having a plurality of phase contacting paths of relatively small cross sectional area connected in parallel, precipitating a part of said material from solution in said solvent in the phase contacting paths of each column, and causing the precipitate in each column to flow therethrough in the same direction as said solution.

12. A process for precipitating a material such as mineral oil from solution in a selective solvent comprising, flowing said solution serially through a plurality of columns, precipitating a part of said material from solution in said solvent in each of said columns, causing the precipitate in each column to iiow countercurrently to the solution passing therethrough, and maintaining at leastone of the phases in each column for at least the most part in lm form and in separate streams.

13. A process comprising at least substantially saturating a selective solvent with mineral oil by countercurrently flowing said solvent and oil through a column while maintaining at least one of said phases for at least the most part in lm form and in separate streams, flowing the solvent with oil in solution produced by said column through a second column, precipitating a part of the dissolved oil in said second column, flowing said precipitate through said second column countercurrently to said solvent, and maintaining at least one of the .phases in said second column for at least the most part in film form and in separate streams.

MERRELL R.Y FENSKE. WILBERT B. MCCLUER. 

